It is common to add fragrance compositions to consumer products to deliver a fresh (or clean) odour to targeted substrates (such as textiles, hard surfaces, skin, hair etc.) and to provide an olfactory aesthetic benefit.
Efforts continue to be made to find improvements in the performance of fragrance compositions, including their in-product shelf life, their delivery effectiveness and their longevity or substantivity on various substrates.
For example, during cleaning processes a substantial amount of fragrance is lost with rinse water and through drying, and it is extremely important to be able to overcome these process conditions and ensure that the fragrance material left on the substrate provides maximum fragrance effect via the minimum amount of material, i.e. there is a need to be able to create highly substantive fragrance materials.
Substantive fragrance ingredients (also known as “enduring perfumes”) are those that effectively deposit onto a substrate in, for example, a cleaning process and are detectable (olfactively) on the wet and subsequently dried substrate. Persons skilled in the art of creating fragrance compositions, usually have some knowledge of particular fragrance ingredients that are substantive (in general, such ingredients are heavy, insoluble and non-volatile).
Fragrance performance may also be enhanced through the use of encapsulation systems to protect and release them in a controlled manner.
Encapsulation systems are usually designed to achieve two objectives.
The first objective relates to the protection of ingredients entrapped in such systems. The second objective is to control, depending on the final application, the release of the entrapped ingredient. In particular, if the entrapped ingredient is volatile, it is important to prevent its release during storage, but at the same time ensuring release of the entrapped volatile ingredient during use. Release is normally triggered by conditions that are typical of such use (e.g. heat, moisture).
An example of such encapsulation technology is embodied in microcapsules filled with perfume, which are commercially marketed by, e.g., Reed Pacific (in Australia), Celessence (in the UK), Hallcrest Inc. (in the US), or Euracli (in France). These microcapsules are adapted to break under friction and provide an instant “burst” of the fragrance when the microcapsules are ruptured. Microcapsules of the aminoplast type are used in the textile industry and include microcapsules that are deposited on the fabric surface during the fabric finishing operation. These microcapsules are generally removed in the course of subsequent domestic washing, but typically can withstand about five washes before the fabric or skin beneficiating ingredients lose their intended effect.
The preparation of microcapsules for encapsulation technology is a known art; preparation methods are, for instance, described in detail in a handbook edited by Simon Benita (“Microencapsulation; Methods and Industrial Applications, Marcel Dekker, Inc. N.Y., 1996), the contents of which are incorporated herein by reference for the preparation techniques described therein.
Further reference is made to a number of patent publications that describe the use of encapsulated fragrance in household applications, such as detergent compositions and in fabric softener products. For example, U.S. Pat. No. 4,145,184 describes detergent compositions that contain perfumes in the form of friable microcapsules. Preferred materials for the microcapsule shell walls are the aminoplast polymers comprising the reaction product of urea and aldehyde.
U.S. Pat. No. 5,137,646 describes the preparation and use of perfumed particles, which are stable in fluid compositions and which are designed to break and release the perfume as the particle is used. This patent describes fabric softener compositions comprising perfume particles comprising perfume dispersed in a solid core comprising a water-insoluble polymeric carrier material. These cores are encapsulated by a friable coating, such coating being preferably an aminoplast polymer.
Encapsulated fragrance composition particles may be mixed into, for example, laundry compositions. Perfume may be combined with water-soluble polymer(s) to form particles that are then added to a laundry composition, as described in U.S. Pat. Nos. 4,209,417; 4,339,356; 3,576,760; and 5,154,842.